The present invention relates to battery powered devices. More particularly, the present invention is a device and method of controlling the selection and control of electrochemical cells in battery powered devices to achieve greater efficiency. The invention has particularly beneficial features when incorporated into hand-held flashlights for personal use.
Many electrical powered devices, particularly small portable electrical devices, employ primary and secondary electrochemical cells or batteries for energy storage and delivery. A primary cell is used once and replaced, while a secondary cell may be discharged and recharged multiple times. Both types of cells include many different designs and chemistries for different applications. Most electrically powered devices have a minimum supplied voltage below which continued use is generally considered impractical or undesirable. The output voltage provided by electrochemical cells decreases over time as the energy stored is released to the powered device. When the cell output voltage falls below the device minimum voltage, the cell is discarded, or must be recharged if a secondary cell. Typically in both cases, but particularly with primary cells, significant stored energy remains in the cell. In the case of primary cells, this energy is entirely wasted. A flashlight provides a good example of this. Incandescent bulbs in flashlights operate optimally within a range of applied voltages. Above a maximum voltage the filament in incandescent bulbs will quickly burn out and cease to function. Below a certain voltage range, the bulb light output falls significantly and is insufficient for most uses. This range of useful voltages is particular to each bulb design. In a battery powered flashlight, the cell or cells used are combined to provide, when the cells are new, a voltage somewhat below the maximum voltage of the flashlight bulb. As the flashlight is used, the output voltage of the cells fans as their energy is expended. The rate at which voltage decreases with energy output varies with the load on the cell and the particular chemistry of the cell. At some point, the output voltage of the cells falls to a level that provides insufficient illumination from the flashlight. Although often considered at this point xe2x80x9cdrainedxe2x80x9d or without power, in fact it is often the case that the individual cells still contain significant energy. If these cells are then replaced and discarded, this energy is lost and the cells must prematurely be treated as waste. This same phenomenon occurs in other battery powered devices.
Disposal of spent primary electrochemical cells is viewed as a significant problem for many reasons. First, the materials in the cells, and their value, is lost when the cells are discarded. Disposal of primary cells also adds to landfill volume. The most significant problem with electrochemical cell disposal is the potential ground water contamination due to leaching of the often toxic materials incorporated in cells. Efforts are underway throughout the world to reduce the amount of cadmium, lead, and mercury and other toxic materials making their way to landfills as primary cells are disposed. Any increase in utilization of primary cell capacity will reduce waste volume from the disposal and replacement of cells.
What is needed is a method and device for using electrochemical cells in which the full capacity of the cells is used before the cells need be replaced, thereby saving the environment for the world""s future.
The present invention provides a device and method for powering a device with various subsets of a group of electrochemical cells, while allowing an unconnected group to remain unconnected from any load. The unconnected cells are enabled to autoregenerate thereby increasing their useful capacity. Devices according to the present invention have two or more cells and means of selecting and connecting one or more cells to a powered device. The number of combinations of cells connected to the powered device is greater than the number of cells. In one embodiment, multiple push button selector switches on a flashlight each connect a cell in series to a flashlight bulb. Each cell may be thereby independently connected or disconnected from the flashlight bulb. In a preferred embodiment, an overvoltage switch connected to the powered device and a relay is provided to ensure that a user selected cell combination does not deliver a combined voltage greater than a limit for incurring damage to the powered device. A simple power switch may also be provided to isolate the cells from the powered device. The power switch may also be incorporated into a cell selection switch.
A unique method of operation according to the present invention includes:
retaining N greater than 1 electrochemical cells with a electrically powerable light emitting device;
sequentially connecting unique combinations of cells to the light emitting device while observing the emitted light and selecting a desired emitted illumination; monitoring an output voltage from each combination of cells; and when the output voltage exceeds a predetermined limit, automatically disconnecting the cells from the light emitting device. A key element of the overvoltage control is the use of relays or similar devices that absorb power only during switching operations in order to reduce power consumption. The elimination of impeders and other such devices that absorb power continuously during operation of the powered device reduces overall power consumption. The discrete switching operation provides opportunity for autoregeneration in the disconnected cells.
An important characteristic of the structure, and methods of using, the present invention is that the voltage, and therefore the powered device operation, is based upon extemporaneous direct user selection and control. By use of the multiple cell combinations, the user may select various power levels, in the case of a flashlight, various illumination levels. This capability in conjunction with low power consumption and autoregeneration creates unique devices providing more effective power usage. Other benefits and features of the inventions unique devices and methods will become obvious from the following details and examples.